This invention relates to printers and more particularly to a controller for use in various printers in which the pitch between adjacent printing lines can be changed.
When printing text information on a cut sheet of paper and delivering the information by using a printer, layout information indicative of paper size, upper/lower and right/left margins, line pitch and the like is set in an internal controller and the printer is operated to print and deliver the text information in accordance with the layout information. The line pitch is increased for the sake of printing a larger character and is decreased for printing a smaller character so that the printing layout can be balanced. The line pitch information is set in accordance with instructions by the operator.
As exemplarily shown in FIG. 2, the printer is supplied with the line pitch information indicative of a left upper end point 21 of a printable area 20 on a cut sheet and a cursor position 22 at the first line and first column on a character series. The left upper point 21 takes a value specific to the printer which is predetermined for various paper sizes including JIS (Japanese Industrial Standards) A4 size and postal size. The cursor position 22 is determined when commands representative of a text write area and upper/lower and right/left margins are supplied from a host computer to the printer. With the cursor positioned as indicated at reference numeral 22, commands representative of information about a line pitch Lp and a column pitch (character pitch) Cp are transmitted from the host computer and set in the printer under manipulation of the operator to establish a cursor coordinate system referenced to the current cursor position 22 on the basis of the current cursor position 22, line pitch Lp and column pitch Cp. For example, a point denoted by reference numeral 23 indicates a cursor position at i-th line and j-th column (i=2, j=3). Then, a position 24 is set which is offset by a predetermined distance .delta.y from each of the cursor positions 22 and 23 and a base line 25 referenced to the position 24 is set. Hereinafter, the predetermined distance .delta.y will be referred to as cursor/base line distance and the position 24 as base line reference position.
Dot patterns of printing characters 29 and 30 are expanded in reference to the base line reference position 24, with the result that the character 29 is so printed as to lie on the base line 25 and the character 30 is so printed as to be lowered by a predetermined amount from the base line 25.
Generally, the printer is operated to print in accordance with instructions from the host computer such as a personal computer. Individual printing character patterns are printed on printing paper pursuant to a printing layout, the majority of which is determined by the host computer and thus the printer has a smaller degree of freedom and versatility in determining the layout. More specifically, in the conventional printer, when a line pitch setting command representative of line pitch information issued from the host computer is received, a fixed cursor/base line distance .delta.y is set irrespective of the value of line pitch.
For example, JP-A-58-158685 discloses printing control in a printer.
Since the conventional printer always sets the cursor/base line distance to a fixed value irrespective of the magnitude of line pitch, it faces the following problems when the line pitch is changed to change the size of printing character.
More particularly, when, in a printer constructed so as to keep the balance of the printing layout as shown in FIG. 3a, a larger line pitch Lp is set as shown in FIG. 3b for the sake of printing larger characters, the fixed cursor/base line distance .delta.y causes an upper portion of printing character patterns on the first line to protrude from the upper margin or to protrude through the margin region, thereby disturbing the printing balance or overriding printing.
Conversely, when a smaller line pitch Lp is set as shown in FIG. 3c for the sake of printing smaller characters over a large number (M=8 lines) of lines, the cursor/base line distance .delta.y becomes larger than the line pitch with the result that a margin 31 above a printing character series on the first line is excessively widened and the number N of lines on which normal printing is permitted is limited to 7, and therefore N&lt;M and equality between N and M is not achieved.